概念汽车实用英语毛矛概念汽车实用英语U9课件教学.pptVIP

PPT研究院 POWERPOINT ACADEMY * * FUEL INJECTION SYSTEM Sensors monitor the mass of air entering the engine, as well as the amount of oxygen in the exhaust. The ECU uses this information to fine-tune the fuel delivery so that the air-to-fuel ratio is just right. A fuel injector is nothing but an electronically controlled valve. It is supplied with pressurized fuel by the fuel pump in your car, and it is capable of opening and closing many times per second. ? * FUEL INJECTION SYSTEM When the injector is energized, an electromagnet moves a plunger that opens the valve, allowing the pressurized fuel to squirt out through a tiny nozzle. The nozzle is designed to atomize the fuel — to make as fine a mist as possible so that it can burn easily. * FUEL INJECTION SYSTEM The amount of fuel supplied to the engine is determined by the amount of time the fuel injector stays open. This is called the pulse width, and it is controlled by the ECU. The injectors are mounted in the intake manifold so that they spray fuel directly at the intake valves. A pipe called the fuel rail supplies pressurized fuel to all of the injectors. * FUEL INJECTION SYSTEM In order to provide the correct amount of fuel for every operating condition, the engine control unit (ECU) has to monitor a huge number of input sensors. Here are just a few: Mass airflow sensor — Tells the ECU the mass of air entering the engine * FUEL INJECTION SYSTEM Oxygen sensor — Monitors the amount of oxygen in the exhaust so the ECU can determine how rich or lean the fuel mixture is and make adjustments accordingly Throttle position sensor — Monitors the throttle valve position (which determines how much air goes into the engine) so the ECU can respond quickly to changes, increasing or decreasing the fuel rate as necessary * FUEL INJECTION SYSTEM Coolant temperature sensor — Allows the ECU to determine when the engine has reached its proper operating temperature Voltage sensor — Monitors the system voltage in the car so the ECU ca